1. Field of the Invention
The present invention relates to the field of electronic devices. More particularly, the present invention relates to a switching voltage regulator such as a DC--DC converter.
2. Description of Art Related to the Invention
The power supplies in an electronic system (e.g., computer system, peripheral input/output device, etc.) are designed to meet specific power requirements for components employed within the electronic system. These components usually include integrated circuit chips (ICs) which are manufactured to meet nominal operating voltages recognized by the industry. Typically, nominal operating voltages for ICs are either 3.3, 5 or 12 volts ("V").
In those situations where an IC requires a unique nominal operating voltage, a DC--DC converter may be used to convert a direct current ("DC") input voltage to a desired DC output voltage. DC--DC converters may be broadly classified as linear voltage regulators and switching voltage regulators, and switching voltage regulators may be further classified as pulse-width-modulated ("PWM") converters and resonant converters. Switching voltage regulators are often preferred over linear voltage regulators due to their superior efficiency.
Referring to FIG. 1, a conventional DC--DC converter is shown. The DC--DC converter 10 includes a switching regulator circuit 15, a power switching transistor 20, and an output stage 25 that provides a DC output voltage ("V.sub.out ") to an electronic device such as an IC 30. The DC output voltage "V.sub.out ", provided by the output stage 25, is fed back to the switching regulator circuit 15 via signal line 35. The switching regulator circuit 15 is often a commercially available IC that provides a drive signal for switching the power switching transistor 20 "on" and "off" in response to the sensed value of V.sub.out. The switching regulator circuit 15 typically includes an internal oscillator circuit that outputs the drive signal at a fixed frequency and an internal reference. The switching regulator circuit 15 modulates the pulse width of the drive signal to vary the amount of time that the power switching transistor 20 is switched on. When switched on, the power switching transistor 20 supplies a DC input voltage ("V.sub.in ") to the output stage 25. Thus, V.sub.out is a function of the duty cycle of the drive signal and V.sub.in. For example, if the switching regulator circuit 15 causes the power switching transistor 20 to be "on" fifty percent of the time, V.sub.out supplied to the IC 30 by the output stage 25 is approximately equal to 0.5.times.V.sub.in.
Contrary to conventional converters, another type of switching circuit may be made from low-cost components to perform the switching and regulation functions with the accuracy set by a precision reference. This type of circuit would have superior transient response over the conventional switching converters.